Method and apparatus for monitoring underwater echo range and bearing systems



'o. H. SCHUCK 2,456,598 METHOD AND APPARATUS FOR MONITORING UNDERWATERECHO RANGE AND BEARING SYSTEMS Dec. 14, 1948.

Filed'Aug. 31, 1944 Et$2 E Patented Dec. 14, 1948 rawBEARINGv SYSTEMS VOscarBugQScliuck, Belmont, Mass.,-ass ig'nor to V -the-United-S-tates ofAmerica as represented by "'zl -tl'ie' secreta-l yof the NavyApplicationrAugust 31,1944,SerialNo.\55.2,058

Glaims. (Cl. 177 386) This invention relates to a'method'andj app ratusfor monitoring or adjusting and checking echo range and. bearing'systemsused ,fo'robtaining the bearing and range of remotely positioned targetsand, while particularly directedto-systems of the characterusingcompressional wave-energy, may also be applied tosystemsiusingifra'diant or other energy. R

In echo-ranging systems *adaptedfor detecting the bearing and range 'ofunderwater-targets-such asa submarine,intermittentpulses or pings ofcompressional wave 'energy"are 'proiiectedfrom a transducer which'iszcarried underwater by-the searching vessel.

- In one type of system thedesign characteristics of thetransducer"are-suchthat'the' energy is projected therefrom in-arelativelynarrowyconical beam, the axis of the beamiusually beingsubstantially horizontal. --'-Ihe-energ-y' is -:usually at supersonicfrequency 'although it may be--otherwise and is-commonlyreferred toin"the--artas sound even though it be above'" the normally audiblerange. I i

The transducer is mounted for rotation' and the operator thussearchesarourfd *the'f entire underwater horizon in step's of about tieach for targets. At each step,theoperatorsends out an energy pulseandthen waits fona certain length of time, whichdependsuponthe"range-being searched, to ascertain whether or"notan echo.

of the emitted energy- -pulse is obtained? "If no echo is obtained, thetransducer=is-turnedslightly and the process repeated.

If the energy pulseshouldstrike an -underwater target such asasubmarine;-part of 'itiis reflected.

or echoed back to the transducer;"thelatter now being connected tci 'actas anrenergy'receiver. The echoed wave energy pulsejmpinging-upon theelements of the .L transducer I generates .electromotive forces (therein.and 'thesalatter are then put through a"'suitableg'electronic receiverto .pro-

duce audible and/or visual"indicationst6 the operator. The operator bynoting thebearing of the transducer atcwhich ariecho;is;receivedlwillknow that a.. targ et v lies. soniewhenelalpngisuch bearing.

' The speed ofsupersonicenergy in .waterjsLsubstantially constant being..aboutfldOQ .iiards, .per second; .Thus ther-rang-e ofatheytargetlrnanbe computed from the time requ-ired by-stheenc y pulse totravel,fromthectransducerito..thc. iarget wand .baclgagain. r

In order to achieve then-best results mesh) ranging equipment.oithegenrfaLclass described. 1 it isnecessarf'y that. .thelsigniepmducea byithe FMETHOD' A'NDAPPARATUS FOR MONITOR- INGI: UNDERWATER t,ECHO; RANGE I AND returning echo be as strong as possible in. comparisonwith all unwanted disturbances, A such as are produced by'waterbackground,.wateii.lturbulence due'to motion .of the'ship andtransducer,

thermal noise'and vacuum tube noise. Torealize this condition, .iti's,therefore, of .course, necessary. that".the/receivingzsystem be.accurately tuned to the frequency 'being'emitted by the transmittingsystem: This is ,tli'eqonly requirement provided the efliciency of thetransmitting and receiving {transducer or transducers is'substantially;independent of irequencygover the opcrating ranger-This'is"not,"howeyer, the, case ---with the-commonly used; equipments whichuse transducers that are mechanically sharply resonant. With suchtransducers, thef'efiiciencyialls ofi rapidly as the frequency of theemitted or received signal departs, from the mechanical reso- *nant'frequency?"- That istq say; unless the; transducer is -operated at. itsmechanicali; resonant frequency, thestrengthof-the emitted energy will ibe muchbeloW its maximum'which means that the received echo will also beat a level'below maximum.

For example; the transducer orprojector currently used-, knownas-the"QC" type, has anactive element consisting of asteel'disk 15' "indiameter -andabout' an inch' thick, t'ojthe-back of. which are attached-'a'- 'large number of thin "nickel; tubes.

Through magnetostrictiveactioninduced by ourrent-carryingi'coilssurrounding the nickel tubes,

the-diskand tubesystem'is 'setinto vibration at the frequency 'ofvthe'current in theilcoils." The face of the-disk isinacoustic, contactwith, the

*water I and radiates compressional. wave... energy 7 into the waterMaximumtwavej energyincthe waterisobtained when the amplitude ofvibration ofthe disk-tube system is,,a..maximum; .that is,

at the frequency ormechanicalresonancei, As a receivejr, thjesensitivity .isQgreatest at thislsame frequency.

It is, therefore, ,obviously. important v that the ,,,current. suppliedto. the,.transducer .or..projector be of the frequencyof its mechanicalresonance so. that maximumbompressional waveenel -y may be emittedandsmthatthe returning-echdmay have the frequency: (except'iion-Dopplereffects) .of,.maximum reception se'nsitivitm. eUnfortunate-1y, however, the optimum, Ormechanioal resonant frequency isnota.constant value buttvariescwith .changes inaoperatingeconditions. V

Shel-mechanical Tresonant; frequencyt oiethe transducer ,is determinedby-the-elastic;constants fthesteeland nickel inqthelactiveelementszr Ittherefor tto log-expect d thatazchanse'init m perature of the latter-will cause changes in its resonant frequency. Factors affecting thetemperature of the active elements are temperature of the watersurrounding the transducer, magnitude of polarization current whichisrequired to polarize thev nickel tubes to obtain the magnetostrictiveeifect, power being used, length of time after commencing operation ofthe equipment, and duty cycle being used.

The factor capable of causing the greatestvariation is the watertemperature. Quite large changes therein, often as great as 40 F. can beexperienced in going, for instance, from a cold current into a warmcurrent. If the frequency of excitation of the transducersmagnetostrictive elements had been correct for resonance and, therefore,maximum operating efficiency at the cold water temperature, it would nolonger be correct at the warm water temperature. ,For example, on sometransducers, a variation of 40 F. in the operating temperature hasproduced a change in its resonant, frequency as high as 400 cycles.Unfortunately, the sound operator will probably not be aware that achange has taken place in the water temperature and that his equipmentis no longer functioning properly.

It is, therefore, the general object of this invention to provide anovel method of and monitoring apparatus by which the frequency ofoperation of underwater echo ranging equipment of the class describedmay be simply and quickly adjusted to the desirable end that suchequipment may always be operated at its maximum efficiency.

The method comprises three steps in the following order:

an auxiliary or monitor transducer which is adapted to be spaced a fewfeet from the main echo-ranging transducer. Energy picked up by themonitor transducer from the main transducer is fed into a combinedreceiver-transmitter apparatus which maybe operated first as a receiverso that the main transducer may be adjusted to its optimum operatingfrequency. The transmitter portion of the apparatus is then adjusted tothis frequency by beating it against the frequency of the incoming energfrom the main transducer to zero beat. Energy at such frequency thensent out by the auxiliary transducer is picked up by the maintransducer, now being connected to act as an energy receiver, and fedinto the receiver of the main echo-ranging equipment, the receiver thenbeing tuned for maximum response at such frequency By means of thismethod and the'apparatus employed, the sound operator is thus able veryquickly and simply to adjust the frequency of the transmitter oscillatorof the main echo ranging equipment so that the main transducer willoperate at its'optimum frequency and likewise adjust the receiverportion of theequipment so that it will receive with maximum'sensitivityat such frequency. At the same time the operator can measure the actualefiiciency of his apparatus and compare it against the efficiency notedat the time of installation. This will gradually drop due todeteriorating components, but if the capabili ties of the apparatus areknown the operator can judge for himself the urgency of repairs.

A preferred embodiment of the invention is shown in the accompanyingdrawings in which and ll.

Fig. 1 is a circuit diagram of the apparatus, and Fig. 2 is a frontelevation of the control panel of'the auxiliary monitoring apparatusutilized.

Referring now to the drawings, there is shown at l0 a transducer of theQC type described hereinabove which may be contained within a heavilyconstructed spherical housing l l, a portion of the wall of which ismade of sound transparent material such as rubber or thin steel (notshown). This housing is supported at the lower end of a tubular casing12 which projects through the bottom of avessels hull l3 and is adaptedto be rotated so that the transducer Ill may, in operation of theecho-ranging equipment,v be turned through 360.

All of the coils surrounding the nickel tubes in transducer I0 may beinternally connected and a pair of leads [4, l5 brought out to sliprings i6 Connections are. then taken over conductors I 8, l9 to contactsEla of rela ii. For echo-ranging operation, the winding of relay 2| isenergized at predetermined intervals and for a given period during whichit is seen that the output of transmitter 22, usually at supersonicfrequency, is connected through the relay contacts 2la to transducer I 0causing the latter to emit compressional wave energ into the surroundingwater medium.

When relay 2| becomes de-energized, its contacts Zia open. Transmitter22 is thereby disconnectedfrom transducer l0 and receiver 23 isconnected thereto. This places the receiver in readiness to receiveelectrical signals corresponding to the echo of the emitted energy pulseif reflected from an underwater target.

The foregoing apparatus which has been described is conventional and maybe referred to as the main or principal apparatus.

The apparatus for performing the novel method of this invention may bereferre to for convenience asthe monitoring or auxiliary apparatus.It-comprises a second transducer 2 which is positioned adjacent to themain transducer ii). Transducer 24 maybe suspended over the side I .ofthe ship-when it is desired to put it into use.

Preferably, however, it is permanently installed adjacent the maintransducer Hi. It may thus be supported at the bottom of a verticallyadjustable rod 25 which passes through a tubular housing' 26, the latterbeing passed through the hull i3 and provided with a well 29 at itslower end into which the transducer 24 may be drawn up when not in use.V

The design of transducer 2 1, which may also be of the magnetostrictivetype, is preferably such that when its elements are energized, thepattern of the wave energy emitted will be substantially uniform in alldirections in a horizontal plane. One such type of transducer is shownin application Serial No. 519,233 filed January 21, 1944, by FrancisP.'Bundy, Patent No. 2,431,026 granted November 18,1947. Another isdescribed in U. S. Patent No. 1,985,251 issued December 25, 1934, toHarvey C. Hayes.

Transducer 24which may be referred toas the monitor transducer should bemounted near to a distance x found satisfactory,

iMonito ntiansducere2. a .l .f

justable bil :me nswonattenuaterall... 3 ne tedxzbetween; theiputpu of.ttub input to tube as. The putput-zflfiigmpliiiflzafi is a delivered-rtea meter 38.

;1The;transmitteniportion-oietheaunitmpmiirises v an -rnoscillat r 4h,tWhemthetflatterriiseplaced in operationt .oughactionaoficontactsMbwitch cont-Itoljgridt a note *1 yielded by-r; this arrangemen asgrid4-1.4 3a 'ei-manothersampIi-ii 4 output iroma amplifier -43tacts.z3.4'c;of?.switoh 34ft v :atxotheriampiifiep tube 44? Thezbutplil, i plifier 4,4- is then fed zintdaiifludspeaket,45mf2lfhe outputfrequency of:oscillator!limaym adinsted bytuningcapacitor 46; 1:1Inc-Fig. '-2;:which: represents' atir on't felemtion a; of 1118:controlnpanel ofietheecombinedtmeceivertransmitter ":lln'it ilyatheiifrdnt oies'ueakerafl is :i: 1' shown at: theiuppei iflefitiithe leerrfereop t switch 34 is.;i-dentified b eferenceii numeral 45!.-

and shown at: the. lowentlef its intermediate position when adjustingthe outs,

-putfrequencywot oscillator 4| to the frequency of the incoming signalfrom transducer l0; and it is moved to itsmpperripositiom whentransmitting .1 signalsirom transducerlflbaflk ltdtransducer l0.

Operation As explained 'a bovet the novel ihethod for adjusting theoutput frequency from transducer In t ep im m. a ue. r thereonmus neotne transducer of. h .teehejfim fi fl merit 'w 'er vt l tter. .meyhettun si to he. l s aue y wh ch gives max mum tene exeou p t;

2. Adjusting an oscillator in the monitoring apparatus to thefrequenoyeazsbe atained in step 1;

and

:r; ne'liran mi t sat -su ttenii y t la e. r e vi transdu n e theeehoesens ns 34, ioneefunotion of; its zoutput gis :toecombinewith v a;signal: incoming ifromatransduceriu toncentrol 1 acent amplifier 35.,Theoutput from amplifier nfiitered to sipasjse" t m ough 013g heir-aceofm'i'eter 38 v is atmpperrcenters dial 8 atsiiowenmightiisifor rede iay. partic ar t mesecmp esthreelst pt? Mea urin .theiso nclsene eyreesiy'eflai om v in eq-Hipment ;;f;rom=, an rauxiliarys transducerassoate. 'gwitha-theamonitoringequipment and adnstinthe-zreceiverqportion of-the main ,echoeranging equipment to thatsamefrequency.

per-form;step '1, relay 2| .is held energized nsducer ll] thus deliverscompressional ergyintothe Waten-being driven by transmitter 22., at :afrequency} setby the operator whiqh; might, for: example, be the norm ofits a l neratm'erxan Switch lever 41 is now moved to itsdown posiion,-inywhiemposition; the top; and middle coneets ois ontact: set 34:b-inlswitch -34;are opened ndzthe ziddleqandbottom contacts of this set 2simrlarly-ecl'osed; All the other :contacts in remainingscontactsets 'ofswitch 34 remain a hownin Tie-1- With:,switch-lever 4'! in its downposition; the nompressional wave energ emitted. fromtransducentlL-isz-picked up bymonitort transducer 24, hieh energy isthen: converted intocorrespondg electrical signals which feedover'conductors 3:2ijcinto the primary ofjtrans-former 28-. 'The.Iaspondingsignals-produced in the secondary ntnansiormer 28 are thenlapplied through the midd-legantt 110013130111 contacts ofcontact set34a vswitch 34 to the-grid= 33a of amplifier 33. Theimltputg-fromamplifier 33-isapplied'through attenuator 3,1to; the ;grid 35a of thenext adv tuned ItQ' thQ', mechanical resonantfrequency of 4 transducenHbwhichaspreviously: described is troxn; its down-mosttposition to itsintermediate 59- pesitionswhioh' puts; all of the contacts in itsecontactsets inf-the" relation shown in Fig. herchange eta-compared-Withhaving switch 'lnlownaiswto -openthe middle and bottom pnta \contactset-y3 ib in switch 34, andclose emiddle and top oontacts of thisjset.With ese connectionsia D.- C. ,plate potential from a source marked Bisapplied-throughthe middle and1topgcontacts ot contact set34b in switch34 to toot-oscillator 4i to thereby initiate its 7 the latter beingappliedover conductor 129i %rid-36b-of--tube 36. v TubeBS-is-also atthis me ireoeiving; signals i (men gricL36a correspond- Jnggtogthe-compressional wave energy being picked uphya mnsducer a Zhfrom {transducer 10 and; put

hieugh=,amplifiers-33 and 35.

It is thus seen that-'ttubezfiagets one ,signal at theyoutputinequencyofatransducer I II and .a second signal at the output frequencyof oscillator M iTheflresultisthataJoeat noteis yielded fromitflvlillbeifi whichgis-filteredto the grid 43a of ampliheeoutput fromamplifier 43 is then pplied to ethe gridM-Ma of -amplifier 44-via ethe tme-end middleeontacts elf-co tact s t Me in t 5 l. thereby-rimm g oundin the loud pea et-ii-a the requents-rot theiaforesaid beat note. Theoutput frequency from oscillator 4| is then adjusted by turning dial 48(which adjusts capacitor 46) until the note comes practically to zerobeat; that is, until the' indicator needle of meter 38 is made tooscillate as slowly as possible or not at all. At this stage, the needleof the meter indicates the beats, and the significance of this to theoperator is that oscillator 4| is now tuned practically to thesamefrequency as the signal which is being emitted by the maintransducer I0.

iri'tensity of the wave energy emitted by said transducer, adjusting thetransmission frequency of said transmitter unit until said measuredenergy is-a maximum, transmitting energy at said adjusted frequency froman auxiliary source for reception by said transducer and the receiverunit, and tuning said receiver unit until the energy received by it is'amaximum.

To perform step 3, switch lever 41 is moved to its uppermost positionwhich continues the closure of the middle and top contacts of contactset 3417 in switch 84 and now'closes the middle and v transducer 24.This energy is received by the main transducer ll! which, in theparticular embodiment being described, now has been disconnected fromthe transmitter 22 and connected to receiver 23 by ole-energizing thewinding of relay 2!. Receiver 23 is then tuned so as to give a maximumresponse in the visual and/ or aural in- 2. Monitoring apparatus forestablishing the optimum frequency of operation of echo range andbearing equipment, the latter including main transmitter and receiverunits and main transducermeans, said apparatus comprising an auxiliarytransducer'spaced from said main transducer means, an'auxiliary receiverconnected to said auxiliary transducer for receiving signalscorresponding to wave energy emitted by said main transducer means,-asignal strength indicator in the output of said auxiliary receiver, anauxiliary transmitter, and switch means for selectively connecting theoutput from said auxiliary transmitter to an input of said auxiliaryreceiver and to said dicating apparatus which is a part of theconventiona-l equipment comprising receiver unit 23.

Recapitulating, the overall result of the foregoing three steps is thatfirst, by adjusting'the frequency of the transmitter 22, the maintransducer It! has been set to operate at its mechanical resonantfrequency for the particular operating conditions encountered, whichfrequency is that at which the transducer emits maximum sound energy inthe Water. By the aid of the monitoring apparatus 21, oscillator Al hasbeen adjusted to that frequency and has sent wave energy of thatfrequency back to the main transducer 10, such energy being fed into themain receiver unit 23 Which has thereupon been adjusted for optimumreceiving effect of energy at such frequency.

The rapidity with which a complete tuning proc-edure may be carried outis decidedly'favorable. Tests show that this can be done in less thantwenty seconds. An ordinary seaman can be trained to perform thenecessary operations in the sound room, thereby allowing the soundoperator to remain at his post and interrupting the normal sound searchfor only a very short time.

In conclusion, I desire it to be understood that while the foregoingembodiment which has been described is to be preferred, various changestherein may occur to those skilled in the art without departing from thespirit and scope of the invention as defined in the appended claims.

It should be further understood that the invention is applicable toother forms of echo range and bearing systems. For example, in theembodiment described, the main transducer is used both for sendingenergy and receiving its echo but it is evident that the invention maylikewise be used in systems utilizing separate transducers for sendingand receiving energy.

After thus fully describing my invention, I claim:

1. The method of bringing wave energy transmitter and receiver unitsalternatively connected to a transducer to an optimum frequency fortransmitting energy therefrom and receiving energy at said optimumfrequency whichcons'ists of the steps of measuring at a selectedposition in space with reference to the transducer the auxiliarytransducer.

3. Monitoring apparatus for establishing the optimum frequency ofoperation of echo range and bearing equipment, the latter including maintransmitter oscillator and receiver units and main transducer means,said apparatus comprising an auxiliary transducer spaced from said maintransdu'cer means, an auxiliary receiver connected to said auxiliarytransducer for receiving signals corresponding to wave energy emittedfrom said main transducer means, and said receiver including "a mixerstage, a signal strength indicator in the output of said auxiliaryreceiver, an auxiliary transmitter oscillator, and switch means forselectively connecting the output from said auxiliary oscillator intosaid receiver mixer stage and to said auxiliary transducer.

4. The method of bringing wave energy transmitter and receiver unitsprovided with radiation emitting and responsive means to an optimumfrequency for transmitting energy therefrom and J receiving energy atsaid optimum frequency which consists of the steps ofmeasuring at aselected positionin space with reference to said means the intensity ofthe wave energy emitted by said means, adjusting the transmissionfrequency of said transmitter unit until said measured energy is amaximum, transmitting energy at said adjusted frequency from anauxiliary source for reception by said means and said receiver unit,

- and tuning said receiver unit until the energy received'by it is amaximum.

OSCAR HUGO SCI-IUCK.

REFERENCES CITED The following references are of record in the file ofthis patent:

.UNITED STATES PATENTS I Number Name Date 1,321,197 Fay Nov. 11, 19191,518,123 Lawther Dec. 2, 1924 2,308,390 Ritzmann Jan. 12, 19432,355,826 Sharpe Aug. 15, 1944 2,363,583 Gilman Nov. 28, 1944 2,405,814Brannin Aug. 13, 1946 2,421,016 Deloraine et al May 27, 1947 y, FOREIGNPATENTS Number Country Date 3,934- Great Britain Jan. 15, 1914 297,998Germany Apr. 1, 1921

